Java中的 LinkedHashMap containsKey() 方法及示例
Java.util.LinkedHashMap.containsKey() 方法用于检查特定键是否被映射到 LinkedHashMap 中。它将键元素作为参数,如果该元素在映射中映射,则返回 True。
句法:
Linked_Hash_Map.containsKey(key_element)
参数:该方法仅采用一个参数key_element ,该参数引用应该在映射中检查其映射的键。
返回类型:如果检测到密钥的存在,则该方法返回布尔值 true,否则返回 false。
示例 1:将字符串值映射到整数键。
Java
// Java code to illustrate the containsKey() method
import java.util.*;
public class Linked_Hash_Map_Demo {
public static void main(String[] args)
{
// Creating an empty LinkedHashMap
LinkedHashMap li_hash_map =
new LinkedHashMap();
// Mapping string values to int keys
li_hash_map.put(10, "Geeks");
li_hash_map.put(15, "4");
li_hash_map.put(20, "Geeks");
li_hash_map.put(25, "Welcomes");
li_hash_map.put(30, "You");
// Displaying the LinkedHashMap
System.out.println("Initial Mappings are: " + li_hash_map);
// Checking for the key_element '20'
System.out.println("Is the key '20' present? " +
li_hash_map.containsKey(20));
// Checking for the key_element '5'
System.out.println("Is the key '5' present? " +
li_hash_map.containsKey(5));
}
}
Java
// Java code to illustrate the containsKey() method
import java.util.*;
public class Hash_Map_Demo {
public static void main(String[] args)
{
// Creating an empty LinkedHashMap
LinkedHashMap li_hash_map =
new LinkedHashMap();
// Mapping int values to string keys
li_hash_map.put("Geeks", 10);
li_hash_map.put("4", 15);
li_hash_map.put("Geeks", 20);
li_hash_map.put("Welcomes", 25);
li_hash_map.put("You", 30);
// Displaying the LinkedHashMapHashMap
System.out.println("Initial Mappings are: " + li_hash_map);
// Checking for the key_element 'Welcomes'
System.out.println("Is the key 'Welcomes' present? " +
li_hash_map.containsKey("Welcomes"));
// Checking for the key_element 'World'
System.out.println("Is the key 'World' present? " +
li_hash_map.containsKey("World"));
}
}
输出:
Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
Is the key '20' present? true
Is the key '5' present? false
示例 2:将整数值映射到字符串键。
Java
// Java code to illustrate the containsKey() method
import java.util.*;
public class Hash_Map_Demo {
public static void main(String[] args)
{
// Creating an empty LinkedHashMap
LinkedHashMap li_hash_map =
new LinkedHashMap();
// Mapping int values to string keys
li_hash_map.put("Geeks", 10);
li_hash_map.put("4", 15);
li_hash_map.put("Geeks", 20);
li_hash_map.put("Welcomes", 25);
li_hash_map.put("You", 30);
// Displaying the LinkedHashMapHashMap
System.out.println("Initial Mappings are: " + li_hash_map);
// Checking for the key_element 'Welcomes'
System.out.println("Is the key 'Welcomes' present? " +
li_hash_map.containsKey("Welcomes"));
// Checking for the key_element 'World'
System.out.println("Is the key 'World' present? " +
li_hash_map.containsKey("World"));
}
}
输出:
Initial Mappings are: {Geeks=20, 4=15, Welcomes=25, You=30}
Is the key 'Welcomes' present? true
Is the key 'World' present? false
注意:可以对任何类型的映射执行相同的操作,这些映射具有不同数据类型的变化和组合。